The present invention relates to a container with tamper-evident and pre-lockable closure assembly, and in particular to a container with a screw cap of a type having attached thereon an index ring to provide an authenticity seal, and being provided with snap-in projections on the outside of a raised container neck forming the inlet or outlet opening, with flexible tongues disposed on the index ring engaging non-detachably behind the snap-in projections in such a way that several thin bridge portions formed between the screw cap and the index ring and serving as predetermined breaking points are severed when the screw cap is unscrewed.
The container may be a sheet metal container, for example a pail made of tinplate with a fill and drain opening in the cover or a container made of sheet steel; the container may preferably also be manufactured from plastic material and serve as a container for mineral oil made by blow-molding; a hobbock, a fassett, a storage container, or a plastic container, such as e.g. a bunged drum or a wide-necked drum (lidded drum) having a drum lid and a tension ring closure. Such containers have at least one fill and drain opening in their top bottom or in a separately attached lid which is closed off by a screw cap. The screw cap may be formed e.g. for a bunged drum or for a drum lid with a bunghole, as a bung plug.
It is known to provide screw caps for canisters with a separate, prefabricated push-on index ring serving as tamper-evident safety mechanism which breaks along predetermined breaking points in form of thin bridge portions when the screw cap is released and unscrewed for the first time. This is disadvantageous because the index ring requires provision of a separate mold for carrying out the separate injection molding process. The index ring must be attached separately and may fall off e.g. upon handling during the filling operation, i.e. the index ring is not reliable for automatic handling.
Also known are screw caps for canisters with integrally molded index ring; these screw caps, however, are made of plastics of low or intermediate molecular weight exhibiting inferior mechanical strength at low temperatures. As a consequence, these screw caps did not succeed in an industrial environment since they do not pass approved standards for a drop test at low temperatures.
All known constructions have the further disadvantage that the loosely attached screw cap may become detached as a result of shocks and vibrations during transport from the manufacturer to the filling station and may get lost. Consequently, there is no guarantee that an absolute seal against dust can be maintained e.g. during transport by a truck. In known designs, the authenticity ring or index ring does not remain attached to the neck after the screw cap is removed, and can therefore drop into the subjacent container when emptying the liquid content into a lower container to be filled, i.e. when the container is tilted. Also, a secure locking of the authenticity ring cannot be ensured during attachment of the screw cap, and the bridge portions between screw cap and index ring alone have to absorb the uneven circumferential load on the authenticity ring (during sequential breakage of the bridge portions) when the screw cap is tightened or unscrewed.